sloa119:
"The traditional switching technique (AD modulation) modulates the duty cycle of a rectangular waveform, such that its average content corresponds to the input analog signal. The bridge-tied load (BTL) outputs are the inverse of each other. AD modulation has no significant common mode content in its output.
The BD modulation switching technique modulates the duty cycle of the difference of the output signals such that its average content corresponds to the input analog signal. The bridge-tied load (BTL) outputs are not the inverse of each other. BD modulation has significant common mode content in its output."
With 3116 the outputs do not cancel across a filterpart between the +/- outputs (differential filterpart). For 3116 you need commonmode filtering.
Now for 7498/AD modulation: quote from company/division bought by STM:
"There are two different snubbers that Apogee recommends, a differential snubber and a common-mode snubber. The differential snubber uses a single resistor and capacitor in series in between the two outputs signals; this snubber gives a lower part count but produces slightly higher harmonic distortion on the output. This snubber can also only be used for full-bridge (BTL) outputs. The common-mode snubber uses a resistor and capacitor in series from each output to ground; this snubber uses twice as many parts as the differential snubber, but produces less harmonic distortion on the output"
To improve distortion you could better copy TI snubbers and remove STM snubbers.
I am really curious of the Zobel across the two L inputs is what is responsible for the astonishing bass clarity I hear compared to my 3116 without this circuit. The two amps are also different in that the 7492 doesn't utilize bootstrap caps. The transistor topology is completely different. So it may just be that which is responsible. I have heard that good bootstrap caps make a difference in 3116 and I have been too lazy to mod that. I wonder I had modded mine to good quality bootstrap caps there would be a big difference in bass clarity?
Anyhow, it does seem that if the switching transistors are presented with a constant impedance load as result of Zobel, the dynamic and punch would be better as more current can flow as result of fixed impedance that doesn't spike at a certain frequency. Although the switching frequency is fixed.
Anyhow, it does seem that if the switching transistors are presented with a constant impedance load as result of Zobel, the dynamic and punch would be better as more current can flow as result of fixed impedance that doesn't spike at a certain frequency. Although the switching frequency is fixed.
like I said, here bass clarity and power/amount of bass 3116 exceeds the STM's, but they can't drive low impedance loads, treble suffers too
there is a difference in bass between other amps that can drive my speakers and 3116 and between 3116's, in general 3116 is clearer and tighter, thinner than class AB or my Choco liteamp. Some 3116 boards somehow cancel bass below certain frequencies.
there is a difference in bass between other amps that can drive my speakers and 3116 and between 3116's, in general 3116 is clearer and tighter, thinner than class AB or my Choco liteamp. Some 3116 boards somehow cancel bass below certain frequencies.
That's the first response which even comes close xrk.
Again. Its not there for any filtering. Its there to control any effect the IC sending multiple frequencies at the same time causes L to "induce and has effect on resistance that the IC legs are seeing from it. Remember that with a voice coil (what's the passive component model of a driver? Isn't it RLLCR) resistance varies with frequency. As the L coil, it also creates varying resistance with frequency which the IC output legs have to work against.
This is becoming hard work. Read the 3 internet links I posted. They explain enough between the.
Here's a question. Why do speaker manufacturers place these filters across terminals?
Put it this way. In the side by side test with both 8Ohm paper coned 1978 8inch woofers I came to the conclusions already mentioned, but neglected to say one thought......which was this......
The woofer without this LC snubber needs a tweeter to fill in detail, hopefully it would rid it of a muddled sound.
Listening to the side with the LC snubber I thought that if this was the only mod that was possible to do to the amp I could quite happily live with the woofer without tweeter as the sound improved in detail that much, without losing any overall sound.
Again. All I can suggest to those not believing what I am saying, is test it for yourselves on LTspice and 3116 if you dare. I might have opened a whole new avenue of questions, as I have the feeling that with an optimised pre-LC zobel the larger values of Inductors that the equations work ou as may actually be usable after all!!!!!!!
Again. Its not there for any filtering. Its there to control any effect the IC sending multiple frequencies at the same time causes L to "induce and has effect on resistance that the IC legs are seeing from it. Remember that with a voice coil (what's the passive component model of a driver? Isn't it RLLCR) resistance varies with frequency. As the L coil, it also creates varying resistance with frequency which the IC output legs have to work against.
This is becoming hard work. Read the 3 internet links I posted. They explain enough between the.
Here's a question. Why do speaker manufacturers place these filters across terminals?
Put it this way. In the side by side test with both 8Ohm paper coned 1978 8inch woofers I came to the conclusions already mentioned, but neglected to say one thought......which was this......
The woofer without this LC snubber needs a tweeter to fill in detail, hopefully it would rid it of a muddled sound.
Listening to the side with the LC snubber I thought that if this was the only mod that was possible to do to the amp I could quite happily live with the woofer without tweeter as the sound improved in detail that much, without losing any overall sound.
Again. All I can suggest to those not believing what I am saying, is test it for yourselves on LTspice and 3116 if you dare. I might have opened a whole new avenue of questions, as I have the feeling that with an optimised pre-LC zobel the larger values of Inductors that the equations work ou as may actually be usable after all!!!!!!!
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😀 If it is close you maybe need to read again. Passive loudspeakers mostly do not have ground themselves, some actives do have gnd and those could be death of unprotected bridged amplifiers.
I've seen the source our disagreement on this based on the ad/bd modulation description.
they talk of outpuit goes to ground to stop high switching frequencies. same with bootstrap mod.
this is different place, different reson, and different action.
i gotta take kids to fair, so will elaborate a little later.ts to amp. that is where
they talk of outpuit goes to ground to stop high switching frequencies. same with bootstrap mod.
this is different place, different reson, and different action.
i gotta take kids to fair, so will elaborate a little later.ts to amp. that is where
OK. Kids went fair in record time, so I can respond.....if I remember everything.
So, the data sheets and descriptions of AD and BD modulation and the different output filter topologies......
Thats all I should really need to say. The answer is in there. One word........ OUTPUT.
To elaborate, that whole discussion regarding the explanations of AD & BD filter types is based on output filters.
If you wish to disagree, I would suggest that in that case the bootstrap snubber mod does not work, and so many of you have carried it out, agree with each other that it improves the sound. When in fact the mod would be "fools gold". But it clearly isn't as a few have posted evidence.
But the equivelant circuit of bootstrap mod is in the output filter already, identical it is because it is going to GND. It's sole purpose is to filter the high switching frequencies out of the circuit to GND, so why do it in another place?
Well clearly, its not that simple as in between the the output zobel, and bootstrap mod is the LC filter, and the bootstrap is the other side of LC, which then returns to IC. The bootstrap mod zobel to GND clearly removes high frequency before LC and also prevents from returning into IC gate, so why the need for the output filter zobel?
Looking at it from this direction, relying on what the data sheets etc says, the need for bootstrap mod and output filter together make no sense either.
But, and here's the big difference. The pre-LC zobel mod I am suggesting for 3116, as per 7492 schematic, is not in the output filter as it does not go to GND. The role of the pre-LC is not to filter switching frequencies to ground. Its clearly not there to minimise emi in the speaker wires.
That's why those references don't apply.
This layout and placement of zobel/Boucherot cell is exactly as placing it across terminals of speaker. It works in both directions.
First, it controls the resistance of the coil that the component/output before it sees. So, a steady state resistance to work against rather than a varying resistance with frequency, as is the side effect of a voice coil, or inductor coil. We have to remember at this stage freq range is only regulated by IC from very low fc right up to switching frequency (apart from top which the bootstrap mod helps removing). And, it is switching frequency at this point, so much happening. It isn't until it goes through LC that you have tamed the frequencies required for your output. That's a lot of varying frequency with varying resistance.
So, this is one purpose of the Boucherot cell here. To tame the resistance from variation seen by the IC.
Secondly, there is no potential across this circuit, and it acts on the coil with the current passing in either direction in exactly the same way. Which leads to third reason
Thirdly, the circuit here also works on the component after, as with speaker. As coils create magnetic flux through inductance they are capable of energy storage, and can act like a battery, for short periods like a huge capacitor I suppose. But we don't want energy stored in the inductor as we need the best rise and fall we can get, i.e. response, nice and fast in low ultra seconds, and accurate. If the coil contains a store of energy from inductance, the energy is in between IC and output filters, and the varying voltage created by IC outputs has to negotiate this, which it will not do accurately. If I pour salt into the top of a half full salt shaker, is it that very same salt which I poured in that comes out first? Even if some of the salt gets through first it will still be muddled together with some salt already in the shaker!
This apparently is what the zobel across the coil prevents. It prevents the coil from accumulating a store of energy within its magnetic flux. Which in return should allow the flow of energy, or current straight through, improving response.
I believe this is what's happening with this circuit. It is a cumulation of all the info I have been able to gather on zobels and Boucherot cells, as well as through researching pllxo.
So, the data sheets and descriptions of AD and BD modulation and the different output filter topologies......
Thats all I should really need to say. The answer is in there. One word........ OUTPUT.
To elaborate, that whole discussion regarding the explanations of AD & BD filter types is based on output filters.
If you wish to disagree, I would suggest that in that case the bootstrap snubber mod does not work, and so many of you have carried it out, agree with each other that it improves the sound. When in fact the mod would be "fools gold". But it clearly isn't as a few have posted evidence.
But the equivelant circuit of bootstrap mod is in the output filter already, identical it is because it is going to GND. It's sole purpose is to filter the high switching frequencies out of the circuit to GND, so why do it in another place?
Well clearly, its not that simple as in between the the output zobel, and bootstrap mod is the LC filter, and the bootstrap is the other side of LC, which then returns to IC. The bootstrap mod zobel to GND clearly removes high frequency before LC and also prevents from returning into IC gate, so why the need for the output filter zobel?
Looking at it from this direction, relying on what the data sheets etc says, the need for bootstrap mod and output filter together make no sense either.
But, and here's the big difference. The pre-LC zobel mod I am suggesting for 3116, as per 7492 schematic, is not in the output filter as it does not go to GND. The role of the pre-LC is not to filter switching frequencies to ground. Its clearly not there to minimise emi in the speaker wires.
That's why those references don't apply.
This layout and placement of zobel/Boucherot cell is exactly as placing it across terminals of speaker. It works in both directions.
First, it controls the resistance of the coil that the component/output before it sees. So, a steady state resistance to work against rather than a varying resistance with frequency, as is the side effect of a voice coil, or inductor coil. We have to remember at this stage freq range is only regulated by IC from very low fc right up to switching frequency (apart from top which the bootstrap mod helps removing). And, it is switching frequency at this point, so much happening. It isn't until it goes through LC that you have tamed the frequencies required for your output. That's a lot of varying frequency with varying resistance.
So, this is one purpose of the Boucherot cell here. To tame the resistance from variation seen by the IC.
Secondly, there is no potential across this circuit, and it acts on the coil with the current passing in either direction in exactly the same way. Which leads to third reason
Thirdly, the circuit here also works on the component after, as with speaker. As coils create magnetic flux through inductance they are capable of energy storage, and can act like a battery, for short periods like a huge capacitor I suppose. But we don't want energy stored in the inductor as we need the best rise and fall we can get, i.e. response, nice and fast in low ultra seconds, and accurate. If the coil contains a store of energy from inductance, the energy is in between IC and output filters, and the varying voltage created by IC outputs has to negotiate this, which it will not do accurately. If I pour salt into the top of a half full salt shaker, is it that very same salt which I poured in that comes out first? Even if some of the salt gets through first it will still be muddled together with some salt already in the shaker!
This apparently is what the zobel across the coil prevents. It prevents the coil from accumulating a store of energy within its magnetic flux. Which in return should allow the flow of energy, or current straight through, improving response.
I believe this is what's happening with this circuit. It is a cumulation of all the info I have been able to gather on zobels and Boucherot cells, as well as through researching pllxo.
i understood what you guys are talking about from X's explanation in the 3116 thread.
i can confirm, that my red and black 7498 have that filter onboard.
i posted a diagram of the output filter of the black board in another thread.
i can confirm, that my red and black 7498 have that filter onboard.
i posted a diagram of the output filter of the black board in another thread.
Comparison Measurement and Sound Clips of TDA7492 vs TPA3116
More info over in the the TPA3116 thread here:
http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp-727.html#post4357821
Note that sound clip files need to be renamed to .mp3 before listening.
Sound Clips in this post:
http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp-727.html#post4357835
Measurement looks like this (TDA7492 is grey line):
More info over in the the TPA3116 thread here:
http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp-727.html#post4357821
Note that sound clip files need to be renamed to .mp3 before listening.
Sound Clips in this post:
http://www.diyaudio.com/forums/class-d/237086-tpa3116d2-amp-727.html#post4357835
Measurement looks like this (TDA7492 is grey line):
i had the big red 7498 powering a small outdoor setup over the last weekend.
one channel played a 10" woofer the other a tweeter horn.
it obviously gets much less warm than the cheap 7492.
those chips are super efficient.
it played at ~19.5V with the woofer at max output (the 105db tweeter of course not at max).
within 15hrs my sla batteries dropped from 6.5V to 6.35V.
i have the impression that the board with the big inductors handles bass much better than the 7492 with the tiny inductors.
hops and hemp didn't want me to do the comparison with the 7492 i had brought, too.
one channel played a 10" woofer the other a tweeter horn.
it obviously gets much less warm than the cheap 7492.
those chips are super efficient.
it played at ~19.5V with the woofer at max output (the 105db tweeter of course not at max).
within 15hrs my sla batteries dropped from 6.5V to 6.35V.
i have the impression that the board with the big inductors handles bass much better than the 7492 with the tiny inductors.
hops and hemp didn't want me to do the comparison with the 7492 i had brought, too.
Thanks, Mooly. I believe posts 92 thru 98 are also related to the new thread and should be moved as well.
TDA7492 on Ref All Horn System
I just tested out these amps on my reference synergy and front loaded bass horn 30Hz to 20kHz 3-way system. It sounds fantastic - super low distortion bass with great impact, crystal clear highs. Have a listen... (change .asc to .mp3 extension to listen)
Sounds so good I just ordered two more boards for $6.58ea on Aliexpress 😀
http://www.aliexpress.com/snapshot/6730262625.html
I just tested out these amps on my reference synergy and front loaded bass horn 30Hz to 20kHz 3-way system. It sounds fantastic - super low distortion bass with great impact, crystal clear highs. Have a listen... (change .asc to .mp3 extension to listen)
Sounds so good I just ordered two more boards for $6.58ea on Aliexpress 😀
http://www.aliexpress.com/snapshot/6730262625.html
Could you please point a new guy to a suitable (240V) pwr supply to match this amp (preferably on ali)? Actually, it doesn't have to be aliexpress, ebay is fine too (was just thinking about single order/shipping).
Many thanks
Steve
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Look for any cheap 19v 4.6 or even 3.5amp SMPS for laptops. The cheaper the better and don't get ones with grounded 3-prong AC cords (ground loop noise).
This for example from Amazon is sometimes $6 to $8. Cut of jack and strip wires and insert into screw terminal blocks.
http://www.amazon.com/Replacement-Delta-Adapte-Compatible-Numbers/dp/B003VUU1PK
It's all about context. This thread is about a $6 to $8 budget amp - you don't want to waste money on a fancy expensive power supply. Frankly, my $6 SMPS brick sounds fine to me. I have compared to smoother linear regulated supply and not a big difference because the amp is switching PWM scheme. Maybe for a class A, you need quiet supply and it is noticeable. If you notice even Nelson Pass says use of laptop SMPS is fine for ACA class A. He actually says to people who sneer "get over it!" 🙂
Is a $50 power supply better than a $6 SMPS brick ? Probably. Can you hear a difference with a $8 TDA7492? Probably not.
Is a $50 power supply better than a $6 SMPS brick ? Probably. Can you hear a difference with a $8 TDA7492? Probably not.
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